The present invention relates to an absorber for damping undesirable high frequency electromagnetic oscillations in HF and VHF components.
In the case of equipment for generating, amplifying and transmitting high frequency power, such as e.g. UHF power electron tubes or valves, coaxial lines, rectangular waveguides and circular resonators under certain conditions, in addition to the desired fundamental oscillation, harmonic oscillations of the fundamental and parasitic UHF oscillations also occur. Such parasitic oscillations in the UHF range can considerably impair the operation of HF equipment and must necessarily be eliminated.
Particularly in the case of large electron tubes functioning as amplifier tubes and which, due to the construction having closely juxtaposed tubular electrodes, have a considerable oscillation tendency, it is indispensible to damp the UHF oscillations.
Due to the frequency distribution of the parasitic UHF oscillation, a suitable absorber must have high-pass characteristics in a wide frequency band, must be couplable in a stable manner for UHF oscillations and to a great extent, must be direction-oriented, i.e. mode-selective in its absorptive power, so as not to simultaneously impair the useful frequency.
An absorber with high-pass characteristics is known which cannot be coupled in a stable manner. As a result, the absorber is not fully effective and the parasitic oscillations are only inadequately suppressed. In addition, this known absorber is falsely direction-oriented (mode-selective) and excludes another direction orientation due to physical laws. Thus, it is not possible to adequately absorb parasitic UHF oscillations with this known device in arrangements having high oscillation tendencies.
In other cases, it is not possible to use the absorber in the high power density range of the useful frequency due to the fact that it adversely affects the latter.